The present invention relates to a method of manufacturing a permanent magnet from a material which comprises fine crystallites of RE.sub.2 (Fe,Co).sub.14 B, in which method the material is ground, oriented in a magnetic field, densified and subjected to a thermal treatment so as to form a mechanically stable body having optimum magnetic properties by means of liquid phase sintering. RE is to be understood to mean in this connection a rare earth metal or a mixture thereof, for example a Mischmetal. In a generally known composition RE=Nd which may optionally be replaced partly by Dy. Methods of this type are known per se, for example, from European patent application 0153744. It is explained on page 20 of the said patent application that magnetic materials based on iron, boron and a rare earth metal comprise at least 50% by volume of a magnetic phase having a tetragonal crystal structure. The chemical composition of this phase is RE.sub.2 Fe.sub.14 B (wherein Fe may be partly replaced by Co). The magnetic material furthermore comprises a non-magnetic phase which surrounds the grains of the magnetic phase. Said non-magnetic phase consists primarily of rare earth metals. Such a material comprising at least two phases is obtained by preparing an alloy powder starting from a composition which is non-stoichiometric (for example RE.sub.15 Fe.sub.77 B.sub.8) with respect to the composition RE.sub.2 (Fe,Co).sub.14 B and subjecting it to various temperature treatments.
This said method has at least one essential disadvantage. Alloy additions in the form of other rare earth metals with the object of controlling the magnetic and/or other properties change not only the composition of the magnetic phase but also that of the non-magnetic second phase.